1. Field of the Invention
The present invention relates to a spoken document retrieval system designed to retrieve where a user-specified keyword is uttered from spoken documents and to present retrieved results to a user.
2. Description of the Related Art
There have been proposals of technologies disclosed in Japanese Patent Application Publications Nos. 2002-221984, 2002-278579 and 2005-257954 as the technology of retrieving where a user-specified keyword is uttered from spoken documents.
The technology disclosed in Japanese Patent Application Publication No. 2002-221984 involves converting each of spoken documents and a keyword into a sequence of sub-phonemes; and then, retrieving the sequence of sub-phonemes converted from the keyword, from the sequences of sub-phonemes converted from the spoken documents, with use of word spotting method using dynamic programming. The technology disclosed in Japanese Patent Application Publication No. 2002-278579 involves converting each of spoken documents and a search word into a sequence of speech symbols; then, detecting candidate speech periods, with use of a full text retrieval system; and further, subjecting the candidate speech periods to speech recognition using the word spotting method, thereby determining retrieved results. The technology disclosed in Japanese Patent Application Publication No. 2005-257954 involves generating new sequences of phonemes or syllables for a keyword in a way that a phoneme in a sequence of phonemes or syllables generated from the keyword is replaced with another phoneme on the basis of expansion rules determined by statistics of occurrence frequency of phonemes; and perform retrieval by comparing the new sequences of phonemes or syllables with the sequences of phonemes or syllables targeted for retrieval.
Also, there has been a proposal of a method disclosed in Japanese Patent Application Publication No. 2001-125903 as a more general technology of retrieving a data sequence. In the method disclosed in Japanese Patent Application Publication No. 2001-125903, data sets of similar reference data sequences in advance are created by sorting reference data sequences by unit of data. When a data sequence is inputted as a query, one or more data sets similar to each data item in the query are selected from the created data sets. Then, a histogram for each data item in the selected data sets is created in a way that positions, corresponding to the each data item, on the temporal axis in the reference data sequences are each voted in consideration of the temporal order relation between the reference data sequences. Thereafter, a continuous range of the histogram is judged as a retrieved result.